76 PREPARATION AND MOUNTING 
mingled ; the solution and its contents are then poured into 
a paper filter, placed in a glass funnel; the capsule is again 
washed with benzole, until the whole of the gritty particles 
are removed into the filter. A washing-bottle is then sup- 
plied with benzole, and the contents of the filter washed to 
the bottom until the liquid passes off pure, which may be 
tested by placing a drop from the point of the funnel on a 
warm slip of glass or bright platinum, when, if pure, the 
benzole will evaporate without residue or tarnish; if grease 
be present, the washing must be continued until they are 
free from it. After rinsing through weak acid, or alcohol, 
for final purification, the calcareous forms will be ready for 
mounting. 
The filter and its contents may be left to dry spontaneously, 
when the latter can be examined by the microscope. Should 
time be an object, rapid drying may be effected by any of 
the usual methods; one of which, recommended by Mr. 
Dale, is to blow a stream of hot air through a glass tube 
held in the flame of a Bunsen’s burner. The lower the 
boiling-point of the benzole, the more readily can the 
specimens be freed from it. A commoner quality may be 
used, but it is more difficult to dry afterwards. 
Pure benzole being costly, this may appear an expensive 
process; but, with the exception of a trifling loss by 
evaporation, the whole may be recovered by simple dis- 
tillation. The mixture of tallow and benzole being placed 
in a retort in a hot-water, a steam, or a sand bath, the 
benzole will pass into the receiver, and the tallow or other 
impurities will remain in the retort. When the whole of 
the benzole has distilled over, which is ascertained by its 
ceasing to drop from the condenser, the heat is withdrawn 
and the retort allowed to cool before the addition of fresh 
material. Half a dozen to a dozen filters, each with its 
specimen, can be in process at the same time; and the dis- 
tillation of the recovered benzole progresses as quickly as 
the filtration, which was practically proved on the occasion 
named. The process is very dangerous and great caution 
